In a composting toilet, human waste is decomposed by mixing the waste with peat moss, aerating the mixture, and separating the fluids from the solids. One of the factors which will greatly enhance decomposition is simply time. The more the waste is exposed to air and allowed to drain, the greater the decomposition. It is therefore desirable to increase the path of travel inside the mixing drum to thereby increase the residence time of the waste inside the drum. It is also important for the composting toilet to provide means to remove the oldest, most decomposed material from the unit without allowing fresh material to be removed prematurely.
In U.S. Pat. No. 4,664,527, a rotary type tumbler is described which includes an axially positioned auger that conveys mixed livestock feed to a discharge opening at the same end of the tumbler as where the feed enters the tumbler. This arrangement ensures that feed must travel through the length of the tumbler at least twice before being discharged. However, the feed which is admitted to the auger will usually originate from the top of a mound of material collected inside the tumbler. Older material which is adjacent to the tumbler wall does not get delivered until the tumbler is emptied.
One of the problems described in the patent is the difficulty encountered in carrying the mixed feed from the lowermost part of the tumbler after it has been mixed, to the axially positioned auger so that it can be conveyed to the discharge opening. This problem is addressed in the patented invention by providing scoop blades at the rearward end of the tumbler for carrying the mixed feed to an inlet opening for the auger.
The arrangement of an auger positioned axially in a tumbler such as that shown in U.S. Pat. No. 4,664,527 is unsuitable for use in a composting toilet because the mixed materials are discharged from the auger into a chute which is positioned to deliver the mixed materials outside the tumbler.
In a composting toilet, it is preferable to discharge the decomposed waste into a receptacle which is enclosed by a housing for the toilet. In this way, the decomposed waste is hidden from view and is allowed to decompose still further. For this reason, the receptacle is often called a "finishing drawer".
To comply with health standards and regulations, in a composting toilet, a minimum clearance between the toilet seat and the waste level inside the toilet must be provided. With an axially positioned auger, the path of material discharged into a composting toilet could include the auger and the toilet seat would then have to be very high off the ground to provide the necessary clearance. This is clearly impractical. Further, an axially positioned auger occupies space which could otherwise accommodate waste and therefore reduces the effective capacity of the tumbler.
Thus, while the concept of introducing an auger into a tumbler to increase residence time is known, it is not apparent how to apply this advantageously to maximize decomposition of the finished product in a composting toilet.
In U.S. Pat. No. 4,633,535, an auger is provided in a composting toilet but only a small portion of the decomposing waste material is returned to the collecting bowl beneath the seat and this is done in order to introduce microbes for accelerating decomposition. Most of the decomposed material exits at an end of the unit which is remote from the collecting bowl and the waste traverses the length of the unit only once. There is no teaching of using an auger to increase the residence time of waste in the toilet so as to maximize decomposition in the product discharged from the mixer.
An object of this invention is to provide an auger into a mixing drum for a composting toilet in order to increase the residence time of the material being mixed and to maximize decomposition.